Getting Started with 2D Games Using Pyxel (Part 5): Creating Characters with Classes

#python #gamedev #tutorial #pyxel

Creating Characters with Classes

Characters that appear in a game are commonly referred to as sprites.
In this chapter, we will use classes to prepare a common base class for sprites.

You might feel that “classes sound difficult…” at first,

but for now, the goal is simply to treat a character as a single reusable component.

If you want to review classes beforehand, checking

Chapter 12: Let’s Use Classes

will make things smoother.

The complete code is shown at the end of this article.

1. Prepare the Sprite Module

Create a new file named sprite.py and place it in your working folder.
The folder structure should look like this:

# Folder structure
working_folder/
 ├ main.py
 ├ sprite.py   # sprite module
 └ shooter.pyxres

2. Create a Common Sprite Base Class

In the sprite.py file, define a class named BaseSprite.
This class will serve as the common base class for all sprites.

# sprite.py (excerpt)

import pyxel
import math
import random

class BaseSprite:

    def __init__(self, x, y, w=8, h=8):
        """ Constructor """
        self.x = x  # X coordinate
        self.y = y  # Y coordinate
        self.w = w  # Image width
        self.h = h  # Image height

    def update(self):
        """ Update logic """
        pass

    def draw(self):
        """ Drawing logic (implemented in subclasses) """
        pass

3. Create the Player Class

Next, add a ShipSprite class to sprite.py.
This class inherits from BaseSprite and will be used to create the player character.

# sprite.py (excerpt)

# omitted

class ShipSprite(BaseSprite):

    def __init__(self, x, y):
        """ Constructor """
        super().__init__(x, y)

    def draw(self):
        """ Drawing logic """
        pyxel.blt(
            self.x, self.y, 0,
            0, 0,
            self.w, self.h, 0
        )  # Ship

4. Use the Player Class

Now let’s use the player class inside the Game class in main.py.
We will do this in the following three steps.

4-1. Initialize the Player

Create a player object in the constructor of the Game class.

# main.py (excerpt)

# Initialize the player (placed near the bottom center of the screen)
self.ship = sprite.ShipSprite(W / 2, H - 40)

4-2. Update the Player

Update the player object in the update() method of the Game class.

(In this chapter, the goal is to build the structure, so the player will not move yet.)

# main.py (excerpt)

# Update the player
self.ship.update()

4-3. Draw the Player

Draw the player object in the draw() method of the Game class.

# main.py (excerpt)

# Draw the player
self.ship.draw()

Complete Code

Below is the complete code with all features implemented so far.

# sprite.py

import pyxel
import math
import random

class BaseSprite:

    def __init__(self, x, y, w=8, h=8):
        """ Constructor """
        self.x = x   # X coordinate
        self.y = y   # Y coordinate
        self.w = w   # Image width
        self.h = h   # Image height
        self.vx = 0  # Velocity (X direction)
        self.vy = 0  # Velocity (Y direction)

    def update(self):
        """ Update logic """
        self.x += self.vx  # Move in X direction
        self.y += self.vy  # Move in Y direction

    def draw(self):
        """ Drawing logic (implemented in subclasses) """
        pass

class ShipSprite(BaseSprite):

    def __init__(self, x, y):
        """ Constructor """
        super().__init__(x, y)

    def draw(self):
        """ Drawing logic """
        pyxel.blt(
            self.x, self.y, 0,
            0, 0,
            self.w, self.h, 0
        )  # Ship

# main.py

import pyxel
import math
import random
import sprite  # Import the sprite module

W, H = 160, 120

# Game
class Game:
    def __init__(self):
        """ Constructor """

        # Initialize score
        self.score = 0

        # Initialize player
        self.ship = sprite.ShipSprite(W / 2, H - 40)

        # Start Pyxel
        pyxel.init(W, H, title="Hello, Pyxel!!")
        pyxel.load("shooter.pyxres")
        pyxel.run(self.update, self.draw)

    def update(self):
        """ Update logic """

        # Update player
        self.ship.update()

    def draw(self):
        """ Drawing logic """
        pyxel.cls(0)

        # Draw score
        pyxel.text(
            10, 10,
            "SCORE:{:04}".format(self.score),
            12
        )

        # Draw player
        self.ship.draw()

def main():
    """ Main entry point """
    Game()

if __name__ == "__main__":
    main()